1. Field of the Invention
The present invention relates to an image display apparatus and an image scanning apparatus each displaying an image by horizontal and vertical scanning.
2. Description of the Background Art
Various image display apparatuses, such as a laser projector, each displaying an image on a projection surface by projecting a laser beam on the projection surface are put to practical use. Such an image display apparatus scans a laser beam vertically and horizontally to project an image on a projection surface such as a screen.
When the image display apparatus projecting and displaying an image projects the image on the projection surface inclined with respect to a projection optical axis, for example, such distortion that the image originally having a rectangular shape is displayed in a trapezoidal shape is generated. There are various methods for correcting this distortion of the projection image. A method for correcting this distortion of the projection image is disclosed in National Patent Publication Gazette No. 2000-509522, Japanese Patent Laying-Open No. 2006-350370, and National Patent Publication Gazette No. 2008-547054, for example.
National Patent Publication Gazette No. 2000-509522 describes an apparatus for displaying a video image on an inclined projection surface. This apparatus includes a light source for emitting a substantially parallel light bundle for continuously illuminating image points of the video image, which can be modulated, a deflection device for scanning the light bundle in two dimensions, and a control device controlling the intensity modulation for the light bundle and the deflection of the light bundle according to a function obtained through a calculated distortion correction of the image at least with respect to the inclination of the projection surface. This apparatus recalculates line spacings and the density of the image points and displays the image with the recalculated line spacings and density of the image points.
Japanese Patent Laying-Open No. 2006-350370 describes a system including an electronic correction unit for receiving input image data and generating pre-distorted image data, an image projector for receiving the image data from the electronic correction unit and projecting a pre-distorted optical image corresponding to the pre-distorted image data or a pre-distorted image compensated by projection optical distortion, and an optical reflection assembly being located in the optical path of the pre-distorted optical image to project the optical image on a projection screen. The electronic correction unit of this system encodes the image data to pre-distort the geometry of the input image data such that optical distortion and geometric distortion associated with the image projector and a mirror of the reflection assembly are eliminated in the displayed optical image. This system is configured to eliminate the optical distortion and the geometric distortion when the pre-distorted image is projected on the screen through the projector.
National Patent Publication Gazette No. 2008-547054 discloses an apparatus including a laser for emitting a laser beam, a scanner, a drive circuit for driving a first scan mirror with a drive signal having an amplitude, a feedback circuit for determining the amplitude of the drive signal for each scan line, and a controller for correcting for image distortion. This apparatus is configured to equalize the lengths of a plurality of scan lines of a projected image to each other by adjusting the amplitude of the drive signal employed to sweep a laser beam forming each scan line of the image in order to correct image distortion in an image projection system. This apparatus corrects image distortion by adjusting the lengths of the scan lines.
As described above, a method for correcting the distortion of a projection image by conversely distorting a projected image by processing of image data is proposed. However, conventionally, the load of correction arithmetic processing of the image data is disadvantageously increased.